Steam turbine plant

ABSTRACT

A steam turbine plant of one embodiment includes at least one heater configured to change water into steam to produce high pressure steam and low pressure steam having a lower pressure than the high pressure steam, a high pressure turbine including a turbine or turbines connected to each other in series, and having a first inlet to supply the high pressure steam, a second inlet to supply the low pressure steam and located at a downstream of the first inlet, and an exhaust port located at a downstream of the second inlet, the high pressure turbine being configured to be driven by the steam supplied from the first and second inlets, a reheater configured to heat the steam exhausted from the exhaust port, and a reheat turbine configured to be driven by the steam from the reheater.

CROSS REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2010-88671, filed on Apr. 7,2010, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a steam turbine plant, for example,using solar heat.

Background Art

FIG. 5 is a schematic diagram illustrating an example of a conventionalsteam turbine plant using solar heat. A steam turbine cycle of the plantof FIG. 5 will be described.

A heating medium 118 is transferred to a solar energy collector 119collecting solar heat by a heating medium pump 116. The heating medium118 is, for example, oil. The heating medium 118 is heated by radiantheat of a solar ray 117 at the solar energy collector 119. Subsequently,the heating medium 118 is transferred to a heater 110 as a heatexchanger, and a heating object such as water or steam is heatedtherein. The temperature of the heating medium 118 decreases at theheater 110, and returns to the upstream of the heating medium pump 116.In this way, the heating medium 118 circulates.

In the nighttime when the solar ray 117 may not be received or in theweather of daytime when the solar ray 117 is weak, the heating medium118 accumulated in a heat accumulating tank is circulated or the heatingmedium 118 is circulated to a line heated by an auxiliary boiler.However, the devices or the flow thereof are not shown herein.Meanwhile, in this case, the heating medium 118 bypasses the solarenergy collector 119.

As the solar energy collector 119, various types may be used, but atrough condensing type shown in FIG. 8 is used in many cases. FIG. 8 isa schematic diagram illustrating an example of the trough condensingtype solar energy collector 119. The solar energy collector 119 of FIG.8 condenses the solar ray 117 by a collector mirror 123 and heats asolar energy collection pipe 124. The heating medium 118 circulates inthe solar energy collection pipe 124, and the temperature of the heatingmedium 118 increases by radiant heat transmitted from the solar ray 117to the solar energy collection pipe 124. The upstream and the downstreamof the solar energy collection pipe 124 are respectively connected toheating medium pipes 125. Although the solar energy collection pipe 124is made by the careful examination, the pipe will not be describedherein in detail.

Hereinafter, returning to FIG. 5, the description of the steam turbineplant will be continued.

In many cases, the conventional steam turbine cycle is configured as asingle-stage reheating cycle that includes a high pressure turbine 101and a reheat turbine. An intermediate pressure turbine 102 and a lowpressure turbine 103 are treated as a continuous reheat turbine 113.

The heater 110 includes a boiler 108 which changes water 111 into steam112 by the heat of the heating medium 118, and a reheater 109 whichheats steam for the reheat turbine 113. The water 111 is transferred tothe boiler 108 as a part of the heater 110 by the pump 105, and isheated by the boiler 108 so that the water changes into high pressureturbine inlet steam 112. In FIG. 5, the inlet at the most upstream ofthe high pressure turbine 101 is denoted by the symbol X.

The high pressure turbine inlet steam 112 flows into the high pressureturbine 101 and expands inside the high pressure turbine 101 so that thepressure and the temperature thereof decrease. The high pressure turbine101 is driven by the high pressure turbine inlet steam 112. In the steamturbine cycle using solar heat, the temperature of the high pressureturbine inlet steam 112 is lower than that of the steam turbine cycleusing heat of combusted exhaust gas of fuel in many cases. For thisreason, the high pressure turbine exhaust 114 is not all dry steam asgas, but is partly mixed with a liquid. That is, it is humid steam inwhich the dryness degree is less than 1.

In FIG. 5, a high pressure turbine steam outlet (an exhaust port)located at the most downstream of the high pressure turbine 101 isdenoted by the symbol Y. The high pressure turbine exhaust 114 flowsinto the reheater 109 as a part of the heater 110, is heated by the heatof the heating medium 118, and flows into the intermediate pressureturbine 102.

Intermediate pressure turbine inlet steam 106 expands inside theintermediate pressure turbine 102 so that the pressure and thetemperature thereof both decrease and flows into the low pressureturbine 103. The steam flowing into the low pressure turbine 103 expandsinside the low pressure turbine 103 so that the pressure and thetemperature both decrease and the steam flows to the outside as humidsteam. In this way, the intermediate pressure turbine 102 and the lowpressure turbine 103 are driven as well as the high pressure turbine101.

The steam flowing from the low pressure turbine 103, that is, lowpressure turbine exhaust 115 flows into a condenser 104. In thecondenser 104, the low pressure turbine exhaust 115 is cooled by coolingwater, and is returned to the water 111. The water 111 returns to theupstream of the pump 105. In this way, the water 111 and the steam 112circulate. Meanwhile, seawater or stream water may be used as thecooling water, the water warmed at the condenser 104 may be cooled at acooling tower using atmosphere, and the cooled water may be circulated.

The rotation shafts of the high pressure turbine 101, the intermediatepressure turbine 102, and the low pressure turbine 103 are connected toa power generator 107. The rotation shafts thereof are rotated as thehigh pressure turbine 101, the intermediate pressure turbine 102, andthe low pressure turbine 103 are rotated by the expanding steam. By therotation of the rotation shafts, power is generated in the powergenerator 107.

FIG. 6 is a schematic diagram illustrating another example of theconventional steam turbine plant using solar heat.

In FIG. 6, extraction steam 120 is extracted from one or more turbinesamong the high pressure turbine 101, the intermediate pressure turbine102, and the low pressure turbine 103. A feed-water heater 121 using theextraction steam 120 as a heat source is provided between the condenser104 and the boiler 108, and the water 111 is heated at the feed-waterheater 121. In FIG. 6, the extraction port of the high pressure turbine101 is denoted by the symbol Z. The number of the feed-water heaters 121may be one or more (three heaters are shown in FIG. 6), and theextraction steam 120 may be supplied from one turbine to the pluralityof feed-water heaters 121.

Likewise, the steam turbine cycle of the plant of FIG. 6 includes thereheating cycle and the reheat regeneration cycle as a regenerationcycle, and the conventional steam turbine cycle has that configurationin many cases. The cycle efficiency is improved by the effect of theregeneration cycle. The extraction steam 120 is cooled at the feed-waterheater 121 so that the steam changes into water and is merged with thewater 111 at a drain water pump 122. Meanwhile, in FIG. 6, thedescription of the flow of the heating medium 118 is omitted.

FIG. 7 is a diagram illustrating an example of an expansion line of theconventional steam turbine plant shown in FIG. 5 or 6. In FIG. 7, thevertical axis indicates specific enthalpy, and the horizontal axisindicates specific entropy.

In FIG. 7, a high pressure turbine expansion line 201, a reheat turbineexpansion line 202, and a saturation line 203 are shown. Since theintermediate pressure turbine 102 and the low pressure turbine 103 arethe continuous reheat turbine, the expansion line related to the turbineis one expansion line.

In FIG. 7, a high pressure turbine inlet point 204, a high pressureturbine outlet point 205, a reheat turbine inlet point (an intermediatepressure turbine inlet point) 206, and a reheat turbine outlet point (alow pressure turbine outlet point) 207 are shown.

In FIG. 7, the high pressure turbine exhaust 114 is heated at thereheater 109 up to a temperature equal to that of the high pressureturbine inlet steam 112. Further, in FIG. 7, when the steam changes fromthe high pressure turbine inlet point 204 to the high pressure turbineoutlet point 205 or changes from the reheat turbine inlet point 206 tothe reheat turbine outlet point 207, the steam changes more than thesaturation line 203. Therefore, the steam is dry steam at the highpressure turbine inlet point 204 or the reheat turbine inlet point 206,and the steam is humid steam at the high pressure turbine outlet point205 or the reheat turbine outlet point 207.

Meanwhile, JP-A 2008-39367 (KOKAI) describes an example of a solar powergeneration facility that includes a solar energy collection deviceheating a liquid thermal medium by the solar ray.

SUMMARY OF THE INVENTION

In a reheating cycle using solar heat, a large amount of the highpressure turbine inlet steam 112 is close to the humid region in thediagrammatic drawing of specific enthalpy-specific entropy, and a largeamount of the high pressure turbine exhaust 114 becomes humid steam. Thehigh pressure turbine inlet steam 112 has, for example, a pressure of100 ata and a temperature of 380° C. At this time, a difference betweenthe temperature of the steam at the inlet of the high pressure turbine101 and the saturation temperature of the pressure of the steam at theinlet of the high pressure turbine 101 is about 70° C. The humid steaminside the high pressure turbine 101 causes moisture loss, and degradesthe turbine internal efficiency. Further, since minute water dropscollide with the surface of the turbine blade, erosion may be generated.

Further, since the steam flowing into the reheater 109 to become theintermediate pressure turbine inlet steam 106, that is, the highpressure turbine exhaust 114 is humid steam, specific enthalpy may notbe specified even when the pressure or the temperature of the steam ismeasured. The specific enthalpy may be specified when the humiditydegree of the steam is measured, but it is difficult to measure thehumidity degree with high precision and simplicity. Therefore, since theamount of heat input from the heater 110 to the turbine cycle may not bespecified, the thermal efficiency of the turbine cycle may not berecognized. Further, since the high pressure turbine exhaust 114 and thelow pressure turbine exhaust 115 are both humid steam at the same time,the turbine internal efficiency thereof may not be specified.

Therefore, there is a demand for a steam turbine plant in which thesteam other than in the vicinity of the outlet of the low pressureturbine 103 is not humid steam.

An aspect of the present invention is, for example, a steam turbineplant including at least one heater configured to change water intosteam to produce high pressure steam and low pressure steam having alower pressure than the high pressure steam, a high pressure turbineincluding a turbine or turbines connected to each other in series, andhaving a first inlet to supply the high pressure steam, a second inletto supply the low pressure steam and located at a downstream of thefirst inlet, and an exhaust port located at a downstream of the secondinlet, the high pressure turbine being configured to be driven by thesteam supplied from the first and second inlets, a reheater configuredto heat the steam exhausted from the exhaust port, and a reheat turbineconfigured to be driven by the steam from the reheater.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating a configuration of a steamturbine plant of a first embodiment;

FIG. 2 is a diagram illustrating an example of an expansion line of thesteam turbine plant shown in FIG. 1;

FIG. 3 is a diagram illustrating another example of the expansion lineof the steam turbine plant shown in FIG. 1;

FIG. 4 is a schematic diagram illustrating a configuration of a steamturbine plant of a second embodiment;

FIG. 5 is a schematic diagram illustrating an example of a conventionalsteam turbine plant;

FIG. 6 is a schematic diagram illustrating another example of theconventional steam turbine plant;

FIG. 7 is a diagram illustrating an example of an expansion line of theconventional steam turbine plant; and

FIG. 8 is a schematic diagram illustrating an example of a troughcondensing type solar energy collector.

DESCRIPTION OF THE EMBODIMENTS

Embodiments of the invention will now be explained with reference to theaccompanying drawings.

First Embodiment

FIG. 1 is a schematic diagram illustrating a configuration of a steamturbine plant of a first embodiment. As for the configuration shown inFIG. 1, the differences from the configuration shown in FIG. 5 will bemainly described.

A heater 110 of the embodiment produces high pressure steam 112 and lowpressure steam 311 having a pressure lower than that of the highpressure steam 112 by changing water 111 into steam by heat of a heatingmedium 118. Furthermore, a high pressure turbine 101 includes a highpressure steam inlet X which is located at the most upstream of the highpressure turbine 101 and a low pressure steam inlet 301 which is locatedat the downstream of the high pressure steam inlet X. In the embodiment,a reheating cycle is configured such that the high pressure steam 112flows from the high pressure steam inlet X and the low pressure steam311 flows from the low pressure steam inlet 301. The high pressureturbine 101 further includes a steam outlet (an exhaust port) Y which islocated at the downstream of the low pressure steam inlet 301 and islocated at the most downstream of the high pressure turbine 101.

The high pressure turbine 101 is driven by steam flowing from each ofthe high pressure steam inlet X and the low pressure steam inlet 301into the high pressure turbine 101. The high pressure steam inlet X isan example of a first inlet of the invention, and the low pressure steaminlet 301 is an example of a second inlet of the invention.

The heater 110 of the embodiment includes two economizers 304 and 305,two evaporators 302 and 303, two superheaters 306 and 307, and areheater 109. In the embodiment, as shown in FIG. 6, a reheatregeneration cycle may be configured in which extraction steam 120 isextracted from the middle position of one or more turbines among thehigh pressure turbine 101, the intermediate pressure turbine 102, andthe low pressure turbine 103, and the extraction steam 120 is used toheat the water 111 at a feed-water heater 121. Furthermore, theextraction steam 120 may be supplied from one turbine to a plurality offeed-water heaters 121.

As shown in FIG. 1, the water 111 is transferred to the first economizer(the low-temperature steam economizer) 304 by the pump 105 and is heatedtherein. Subsequently, the water 111 flows into the first evaporator(the low-temperature steam evaporator) 302, and changes intopre-superheating low pressure steam 310. The pre-superheating lowpressure steam 310 is extracted from a gas portion of an upper steamdrum constituting the first evaporator 302, flows into the firstsuperheater (the low pressure steam superheater) 306, and is furtherheated therein. Accordingly, the pre-superheating low pressure steam 310becomes the low pressure steam 311, and flows into the low pressuresteam inlet 301.

At this time, the pressure of the low pressure steam 311 is higher thanthe pressure of the steam at the turbine stage of the low pressure steaminlet 301. Furthermore, since the low pressure steam 311 is sufficientlysuperheated at the first superheater 306, the temperature of the lowpressure steam 311 is higher than the temperature of the steam at theturbine stage of the low pressure steam inlet 301. Meanwhile, in thecase where a plurality of high pressure turbines 101 are connected toeach other in series instead of the case where only one high pressureturbine 101 is provided as shown in FIG. 1, the turbine stage into whichthe low pressure steam 311 flows may be any high pressure turbine.

On the other hand, second water 309 as a liquid is extracted from alower steam drum constituting the first evaporator 302. The second water309 is boosted and transferred to the second economizer (the highpressure steam economizer) 305 by a second pump 308, and is heatedtherein. Subsequently, the second water 309 changes into apre-superheating high pressure steam 312 in the second evaporator (thehigh pressure steam evaporator) 303. The pre-superheating high pressuresteam 312 is extracted from a gas portion of an upper steam drumconstituting the second evaporator 303, flows into the secondsuperheater (the high pressure steam superheater) 307, and is furtherheated therein. Accordingly, the pre-superheating high pressure steam312 becomes the high pressure steam (the high pressure turbine inletsteam) 112, and flows into the high pressure steam inlet X.

The high pressure steam 112 expands inside the high pressure turbine101, and the pressure and the temperature thereof decrease as it goes tothe downstream of the turbine stage in the axis direction of theturbine. In the embodiment, it is set such that the steam inside thehigh pressure turbine 101 does not change into humid steam at a timepoint of the turbine stage of the low pressure steam inlet 301.

When the steam inside the high pressure turbine 101 is merged with thelow pressure steam 311, the temperature of the steam increases, and thepressure and the temperature of the steam decrease as it goes to thedownstream of the turbine stage. In the embodiment, even when the steaminside the high pressure turbine 101 goes to the final stage of the highpressure turbine 101, the steam may not reach the humid region since thetemperature of the steam increases when the low pressure steam 311 ismerged with the steam. That is, in all stages of the high pressureturbine 101 including the high pressure turbine exhaust 114, the steaminside the high pressure turbine 101 may be maintained as dry steamwithout changing into humid steam.

Accordingly, in the embodiment, the high pressure turbine exhaust 114becomes dry steam. After the high pressure turbine exhaust 114 isexhausted from an exhaust port Y and flows into the reheater 109 so thatit is heated therein, the heated high pressure turbine exhaust 114 flowsinto the intermediate pressure turbine 102.

The steam flowing into the intermediate pressure turbine 102 expandsinside the intermediate pressure turbine 102 so that the pressure andthe temperature thereof decrease, and flows into the low pressureturbine 103. The steam flowing into the low pressure turbine 103 expandsinside the low pressure turbine 103 so that the pressure and thetemperature thereof decrease, and flows to the outside as humid steam.The rotation shafts of the high pressure turbine 101, the intermediatepressure turbine 102, and the low pressure turbine 103 rotated by theexpanding steam are connected to a power generator 107, and power isgenerated in the power generator 107 with the rotation of the rotationshafts.

FIG. 2 is a diagram illustrating an example of an expansion line of thesteam turbine plant shown in FIG. 1.

A pre-merging high pressure turbine expansion line 401 changes from ahigh pressure turbine inlet point 204 to a low pressure steampre-merging point 403, and a post-merging high pressure turbineexpansion line 402 changes from a low pressure steam post-merging point404 to a high pressure turbine outlet point 205, but neither of themreach the humid region. In FIG. 2, the high pressure turbine exhaust 114is heated at the reheater 109 up to a temperature equal to thetemperature of the high pressure turbine inlet steam 112.

In the embodiment, a steam turbine cycle is realized in which the steamother than in the vicinity of the outlet of the low pressure turbine 103is not humid steam without changing the statuses and the properties ofthe steam of the inlets of the high pressure turbine 101 and the reheatturbine 113. Accordingly, the humid steam is not present other than inthe vicinity of the outlet of the low pressure turbine 103. Accordingly,a degradation of the turbine internal efficiency caused by moisture lossmay be prevented, and the turbine cycle performance may be improved.Furthermore, there is no possibility of generating of erosion caused byminute water drops colliding with the surface of the turbine blade otherthan the vicinity of the outlet of the low pressure turbine 103.

Furthermore, since the high pressure turbine exhaust 114 is dry steam,specific enthalpy may be specified by measuring the pressure and thetemperature thereof. Accordingly, the amount of heat input from theheater 110 to the turbine cycle may be specified, and the thermalefficiency of the turbine cycle may be recognized. Furthermore, sincethe turbine of which exhaust is humid steam is not plural, but the lowpressure turbine 103 only, the internal efficiency of each turbine maybe specified.

If a turbine cycle is provided such that the number of the turbinestages from the stage merged with the low pressure steam 311 increasesand the reheat turbine 113 is removed, moisture loss until reaching thepressure of the condenser 104 increases so that the turbine cycleperformance becomes lower than that of any one of the embodiment and therelated art.

Hereinafter, various modifications of the embodiment will be described.

(Expansion Line of Steam Turbine Plant)

FIG. 3 is a diagram illustrating another example of the expansion lineof the steam turbine plant shown in FIG. 1.

In FIG. 2, the steam inside the high pressure turbine 101 does notchange into humid steam at a time point of the turbine stage of the lowpressure steam inlet 301, but changes into humid steam in FIG. 3.

In the case of FIG. 3, when the high pressure steam 112 flows into thehigh pressure steam inlet X, the high pressure steam 112 expands insidethe high pressure turbine 101, and the pressure and the temperaturethereof decrease as it goes to the downstream of the turbine stage inthe axis direction of the turbine. In the case of FIG. 3, the steaminside the high pressure turbine 101 changes into humid steam at a timepoint of the turbine stage of the low pressure steam inlet 301.

When the steam inside the high pressure turbine 101 is merged with thelow pressure steam 311, the temperature of the steam increases so thatthe steam changes from humid steam into dry steam. Subsequently, thepressure and the temperature thereof decrease as it goes to thedownstream of the turbine stage. Even in the case of FIG. 3, it ispossible that the steam inside the high pressure turbine 101 does notreach the humid region even when the steam goes to the steam outlet (theexhaust port) Y of the high pressure turbine 101 at the downstream ofthe low pressure steam post-merging point 404 since the temperature ofthe steam increases when the low pressure steam 311 is merged with thesteam. In the related art, the steam is humid steam from the middleposition of the high pressure turbine 101 to the steam outlet Y.However, in the case of FIG. 3, the steam is humid steam only from themiddle position of the high pressure turbine 101 to the stage mergedwith the low pressure steam 311.

Accordingly, in the case of FIG. 3, the high pressure turbine exhaust114 becomes dry steam. After the high pressure turbine exhaust 114 isexhausted from the steam outlet Y and flows into the reheater 109 sothat it is heated therein, the heated high pressure turbine exhaust 114flows into the intermediate pressure turbine 102.

Here, the expansion line of FIG. 3 will be described in detail.

The pre-merging high pressure turbine expansion line 401 changes fromthe high pressure turbine inlet point 204 to the low pressure steampre-merging point 403, and the post-merging high pressure turbineexpansion line 402 changes from the low pressure steam post-mergingpoint 404 to the high pressure turbine outlet point 205. However, evenwhen the former reaches the humid region, the latter does not reach thehumid region. In FIG. 3, the high pressure turbine exhaust 114 is heatedat the reheater 109 up to a temperature equal to the temperature of thehigh pressure turbine inlet steam 112.

In the case of FIG. 3, the number of stages in which the steam otherthan in the vicinity of the outlet of the low pressure turbine 103becomes humid steam decreases without changing the properties and thestatuses of the steam of the inlets of the high pressure turbine 101 andthe reheat turbine 113. Accordingly, since a degradation of the turbineinternal efficiency caused by moisture loss is prevented compared to therelated art, the turbine cycle performance is improved. Furthermore, thepossibility of generating of erosion caused by minute water dropscolliding with the surface of the turbine blade decreases other than inthe vicinity of the outlet of the low pressure turbine 103. Meanwhile,in the case of FIG. 3, it is considered that erosion is not generated ata flow rate of the steam inside the general high pressure turbine 101.

Furthermore, since the high pressure turbine exhaust 114 is dry steam,specific enthalpy may be specified by measuring the pressure and thetemperature thereof. Accordingly, the amount of heat input from theheater 110 to the turbine cycle may be specified, and the thermalefficiency of the turbine cycle may be recognized. Furthermore, sincethe turbine of which exhaust is humid steam is not plural, but the lowpressure turbine 103 only, the internal efficiency of each turbine maybe specified.

If a turbine cycle is provided such that the number of the turbinestages from the stage merged with the low pressure steam 311 increasesand the reheat turbine 113 is removed, moisture loss until reaching thepressure of the condenser 104 increases so that the turbine cycleperformance becomes lower than that of any one of the embodiment and therelated art.

(Use of Solar Heat)

In the embodiment, the heater 110 produces the high pressure steam 112and the low pressure steam 311 by changing the water 111 into steamusing solar heat. Furthermore, the reheater 109 heats exhaust from thesteam outlet (the exhaust port) Y using solar heat. The solar heat issupplied from a solar energy collector 119 (FIG. 5) in the form of heatof the heating medium 119.

Furthermore, in FIG. 1, the turbine at the upstream of the reheater 109is only one turbine (the high pressure turbine 101). However, aplurality of turbines may be disposed at the upstream of the reheater109 to be connected to each other in series, and the plurality ofturbines connected to each other in series may be set as the highpressure turbine. In this case, the high pressure steam inlet X isdisposed at, for example, the most upstream of the turbine located atthe most upstream of the plurality of turbines, and the steam outlet Yis disposed at, for example, the most downstream of the turbine locatedat the most downstream of the plurality of turbines. Furthermore, thelow pressure steam inlet 301 is provided at any turbines among theplurality of turbines.

Furthermore, in FIG. 1, the high pressure steam 112 and the low pressuresteam 311 are produced by the same heater (the heater 110), but thesteam 112 and 311 may be produced by the different heaters. That is, thehigh pressure steam 112 and the low pressure steam 311 may be producedby one heater or a plurality of heaters.

In the expansion line of FIG. 2, it is set such that the steam insidethe high pressure turbine 101 does not change into humid steam at a timepoint of the turbine stage of the low pressure steam inlet 301, andchanges into humid steam in the expansion line of FIG. 3. Furthermore,in this case, as shown in FIG. 6, a reheat regeneration cycle may beconfigured in which the extraction steam 120 is extracted from themiddle position of one or more turbines among the high pressure turbine101, the intermediate pressure turbine 102, and the low pressure turbine103, and the extraction steam 120 is used to heat the water 111.

In the steam turbine cycle using solar heat, the temperature of the highpressure turbine inlet steam 112 is lower than that of the steam turbinecycle using heat of combusted exhaust gas of fuel in many cases. Forthis reason, there is a large merit that dry steam may be prevented fromchanging into humid steam and the number of stages in which the steaminside the turbine becomes humid steam may be decreased.

(Trough Condensing Type Solar Energy Plant)

In the embodiment, a solar energy collector 119 (refer to FIG. 5), forexample, a trough condensing type shown in FIG. 8 is used. In this case,the trough condensing type solar energy collector 119 may be used incombination with a reheat regeneration cycle shown in FIG. 6.

Due to the actual temperature raising capacity in the condensing typeand the heatproof temperature of oil used as the heating medium 118, theproduced high pressure turbine inlet steam 112 has, for example, apressure of 100 ata and a temperature of 380° C. The high pressureturbine inlet steam 112 is sufficiently close to the humid region in thediagrammatic drawing of specific enthalpy-specific entropy. Therefore,in the trough condensing type, there is a high possibility that the highpressure turbine exhaust 114 becomes humid steam. For this reason, theconfiguration of the embodiment is useful in the case of using thetrough condensing type in that dry steam may be prevented from changinginto humid steam and the number of stages in which the steam inside theturbine becomes humid steam may be decreased.

(High Pressure Turbine Inlet Steam Condition 1)

In the embodiment, for example, a difference between the temperature ofthe steam at the inlet of the high pressure turbine 101 as the turbineat the most upstream side and the saturation temperature of the pressureof the steam at the inlet of the high pressure turbine 101 is set to be100° C. or less, and in this condition, the steam turbine cycle isconfigured. In the case where a difference in temperature is 100° C. orless, the high pressure turbine inlet steam 112 is sufficiently close tothe humid region in the diagrammatic drawing of specificenthalpy-specific entropy. This condition may be applied in combinationwith the reheat regeneration cycle shown in FIG. 6.

The above-described condition may be applied to not only the steamturbine cycle using solar heat, but also the cycle in which the highpressure turbine inlet steam 112 is sufficiently close to the humidregion in the diagrammatic drawing of specific enthalpy-specificentropy, and the same effect as that of the case of using solar heat maybe obtained. Therefore, the turbine may be configured as a thermal powerturbine using a combusted exhaust gas as a heat source, and in thiscase, the heating medium 118 is a combusted exhaust gas.

Meanwhile, in the nuclear turbine, the flow of the heating medium 118 inthe heater 110 is different from the flow shown in FIG. 5 in manypoints.

Furthermore, in the case where a plurality of turbines are disposed tobe connected to each other in series at the upstream of the reheater109, the turbine at the most upstream side among these turbines becomesthe turbine at the most upstream side constituting the steam turbineplant of FIG. 1.

(High Pressure Turbine Inlet Steam Condition 2)

In the embodiment, for example, the steam at the inlet of the highpressure turbine 101 as the turbine at the most upstream side has apressure of 20 ata or more and a temperature of 420° C. or less, and inthis condition, the steam turbine cycle is configured. In the case wherethe steam at the inlet of the high pressure turbine 101 has a pressureof 20 ata or more and a temperature of 420° C. or less, the highpressure turbine inlet steam 112 is sufficiently close to the humidregion in the diagrammatic drawing of specific enthalpy-specificentropy. This condition may be applied in combination with the reheatregeneration cycle shown in FIG. 6.

The above-described condition may be applied to not only the steamturbine cycle using solar heat, but also the cycle in which the highpressure turbine inlet steam 112 is sufficiently close to the humidregion in the diagrammatic drawing of specific enthalpy-specificentropy. The turbine may be configured as a thermal power turbine usinga combusted exhaust gas as a heat source or a nuclear turbine, and thesame effect as that of the case of using solar heat may be obtained.

Meanwhile, in the nuclear turbine, the flow of the heating medium 118 inthe heater 110 is different from the flow shown in FIG. 5 in manypoints.

Furthermore, in the case where a plurality of turbines are disposed tobe connected to each other in series at the upstream of the reheater109, the turbine at the most upstream side among these turbines becomesthe turbine at the most upstream side constituting the steam turbineplant of FIG. 1.

(Steam Turbine Cycle)

The steam turbine plant of the embodiment includes three turbines intotal, that is, the high pressure turbine 101 as the turbine at the mostupstream side, the intermediate pressure turbine 102, and the lowpressure turbine 103 as the turbine at the most downstream side.

In the embodiment, it is desirable that the turbine other than the lowpressure turbine 103 among these turbines is operated so that the steamcirculating inside the turbine is maintained as dry steam withoutchanging into humid steam. In this case, only the low pressure turbine103 is operated so that the steam circulating inside the turbine changesfrom dry steam into humid steam. In this case, the humid steam is notpresent other than in the vicinity of the outlet of the low pressureturbine 103. As a result, a degradation of the turbine internalefficiency caused by moisture loss may be prevented, and the turbinecycle performance may be improved. Further, the possibility ofgenerating of erosion in the high pressure turbine 101 decreases.Furthermore, the internal efficiency of each turbine may be specified.

As described above, in the embodiment, the high pressure steam 112 flowsinto the high pressure steam inlet X of the high pressure turbine 101,and the low pressure steam 311 flows into the low pressure steam inlet301 located at the downstream of the high pressure steam inlet X,thereby operating the high pressure turbine 101. Accordingly, the steaminside the high pressure turbine 101 may be prevented from changing fromdry steam into humid steam, or the number of stages in which the steambecomes humid steam may be decreased.

In the embodiment, since the steam inside the high pressure turbine 101(further, all turbines other than the low pressure turbine 103) isprevented from changing from dry steam into humid steam, a degradationof the turbine internal efficiency caused by moisture loss may bereduced so that the turbine cycle efficiency may be improved. Further,there is no possibility of generating of erosion in the high pressureturbine 101. Furthermore, the internal efficiency of each turbine may bespecified. The same applies to the case where the number of stages inwhich the steam inside the high pressure turbine 101 becomes humid steamdecreases. In this case, a degradation of the internal efficiency of theturbine may be prevented, and the possibility of generating of erosiondecreases.

Hereinafter, a second embodiment of the invention will be described. Thesecond embodiment is a modification of the first embodiment. Therefore,in the second embodiment, the differences from the first embodiment willbe mainly described.

Second Embodiment

FIG. 4 is a schematic diagram illustrating a configuration of a steamturbine plant of the second embodiment. As for the configuration shownin FIG. 4, the differences from the configuration shown in FIG. 1 or 5will be mainly described.

In the embodiment, the passageway of the low pressure steam 311 isprovided with a steam valve 313 that may adjust the flow rate of the lowpressure steam 311 or stop the circulation thereof. In FIG. 4, the steamvalve 313 is provided between the heater 110 and the low pressure steaminlet 301 of the high pressure turbine 101.

The pressure and the temperature of the high pressure turbine inletsteam 112 or the high pressure turbine exhaust 114 are different inaccordance with the flow rate of the high pressure turbine inlet steam112 or the amount of heat input from the boiler 108, and the degreeclose to the humid region is different. For example, in the case ofusing solar heat, the amount of heat input from the boiler 108 changesin accordance with a change of the weather.

If the high pressure turbine exhaust 114 becomes humid steam when thesteam valve 313 is fully closed, the steam valve 313 is opened tocirculate the low pressure steam 311. Accordingly, the high pressureturbine exhaust 114 may be set as dry steam. If the high pressureturbine exhaust 114 is dry steam even when the steam valve 313 is fullyclosed, the steam valve is maintained to be fully closed. When the highpressure turbine exhaust 114 is set as dry steam, the enthalpy lossgenerated by the merging with the low pressure steam 311 may be reducedso that the turbine cycle performance is improved.

Furthermore, when the steam valve 313 is configured as a flow ratecontrol valve, the flow rate of the low pressure steam 311 may beadjusted in accordance with an opening degree of the valve. In thiscase, if the high pressure turbine exhaust 114 becomes humid steam whenthe steam valve 313 is fully closed, the low pressure steam 311 may becirculated by an amount necessary for changing the high pressure turbineexhaust 114 into dry steam. When the high pressure turbine exhaust 114is set as dry steam, the enthalpy loss generated by the merging with thelow pressure steam 311 may be reduced so that the turbine cycleperformance is improved.

In the embodiment, as shown in FIG. 6, a reheat regeneration cycle maybe configured in which extraction steam 120 is extracted from the middleposition of one or more turbines among the high pressure turbine 101,the intermediate pressure turbine 102, and the low pressure turbine 103,and the extraction steam 120 is used to heat the water 111.

The technology of the embodiment may be applied to not only the steamturbine cycle using heat, such as solar heat, but also the cycle inwhich the high pressure turbine inlet steam 112 is sufficiently close tothe humid region in the diagrammatic drawing of specificenthalpy-specific entropy. Therefore, the turbine may be configured as athermal power turbine using a combusted exhaust gas as a heat source,and in this case, the heating medium 118 is a combusted exhaust gas.

Furthermore, in a nuclear turbine, the flow of the heating medium 118 inthe heater 110 is different from the flow shown in FIG. 5 in manypoints.

As described above, in the embodiment, the passageway of the lowpressure steam 311 is provided with the steam valve 313 that adjusts theflow rate of the low pressure steam 311 or stops the circulationthereof. Accordingly, the high pressure turbine exhaust 114 may be setas dry steam by adjusting the flow rate of the low pressure steam 311 orstopping the circulation thereof. Therefore, a degradation of theturbine internal efficiency caused by moisture loss may be prevented,and the turbine cycle performance may be improved. Furthermore, theenthalpy loss generated by the merging with the low pressure steam 311may be removed or reduced by stopping the circulation of the lowpressure steam 311 or circulating it by a necessary amount so that theturbine cycle performance may be improved.

As described above, according to the embodiment of the invention, thesteam turbine plant is provided which is capable of preventing adegradation of the turbine internal efficiency caused by moisture lossand improving the turbine cycle performance.

While examples of specific aspects of the invention have been explainedwith reference to the first and second embodiments, the invention is notlimited to those embodiments.

The invention claimed is:
 1. A steam turbine plant comprising: a heaterconfigured to change water into steam, the heater producing highpressure steam and low pressure steam having a lower pressure than thehigh pressure steam by using heat from a single heat source; a highpressure turbine having a first inlet to supply the high pressure steam,a second inlet to supply the low pressure steam and located downstreamof the first inlet, and an exhaust port located downstream of the secondinlet, the high pressure turbine being configured such that the highpressure steam supplied from the first inlet drives the high pressureturbine, expands in the high pressure turbine, decreases in pressure,and is then merged with the low pressure steam supplied from the secondinlet in the high pressure turbine, and the merged high pressure steamand low pressure steam further drive the high pressure turbine, expandin the high pressure turbine, decrease in pressure, and are thenexhausted from the exhaust port; a reheater located downstream of thehigh pressure turbine and configured to heat the steam exhausted fromthe exhaust port; and a reheat turbine located downstream of thereheater and configured to be driven by the steam from the reheater. 2.The plant of claim 1, further comprising a solar energy collectorconfigured to collect solar heat, wherein the heater and the reheaterare configured to heat the water or the steam to be heated by the solarheat.
 3. The plant of claim 2, wherein the solar energy collector is atrough condensing type solar energy collector.
 4. The plant of claim 1,wherein the high pressure turbine is driven such that a differencebetween the temperature of the steam at the first inlet and thesaturation temperature under the pressure of the steam at the firstinlet is 100° C. or less.
 5. The plant of claim 1, wherein the highpressure turbine is driven such that inlet steam at the first inlet hasa pressure of 20 ata or more and a temperature of 420° C. or less. 6.The plant of claim 1, further comprising: a steam valve configured toadjust a flow rate of the low pressure steam or to stop a circulation ofthe low pressure steam.
 7. The plant of claim 1, wherein a turbine,other than the most downstream turbine among all turbines of the steamturbine plant, is configured to operate such that the steam circulatinginside the turbine is maintained as dry steam.